Long-term consequences of COVID-19 on sleep, mental health, fatigue, and cognition: a preliminary study

Introduction: Post-COVID-19 Syndrome (PCS) is defined as symptoms persisting beyond 12 weeks from the onset of symptoms. Notably, COVID-19 has been associated with long-term effects on the brain and mental health. This cross-sectional study aims to investigate depression, fatigue, sleep quality, and cognitive dysfunction, particularly working memory, in individuals with PCS compared to a healthy control group. Material and methods: Between April and December 2021, 45 COVID-19 individuals and 60 healthy individuals met the eligibility criteria. Demographic information and the Montreal Cognitive Assessment were collected. Two visual working memory tasks, Delayed Match-to-Sample (DMS) and n-back, were performed, along with self-report questionnaires: Beck Depression Inventory, Modified Fatigue Impact Scale, and Pittsburgh Sleep Quality Index. Results: A total of 105 participants were enrolled. Findings reveal that the PCS group exhibited notably higher levels of cognitive impairment (13.3% vs. 1.6%, p = 0.04), depression (53.9% vs. 25.9%, p = 0.03), and sleep disturbances (53.9% vs. 18.6%, p = 0.01) compared to the healthy control group. Sleep latency and sleep duration were particularly affected. No significant differences in working memory function were observed between the two groups (p = 0.90 for DMS and p = 0.98 for n-back). Conclusion: The study highlights the higher prevalence of sleep disturbance, depression, and cognitive impairment in the PCS phase, with inflammation likely playing a significant role. Moreover, the study suggests that untreated depression and sleep disturbances may pose long-term risks for dementia. Understanding the underlying mechanisms is crucial for developing effective interventions and support for individuals recovering from the infection. Prospective longitudinal studies with larger and more diverse samples are warranted to confirm and expand upon these findings. © The Author(s) 2025.